How to use Java to Combine Multiple PDF Files

wsimport https://localhost:41734/Muhimbi.DocumentConverter.WebService/?wsdl -d src -Xnocompile -p com.muhimbi.ws

package com.muhimbi.app;

import com.muhimbi.ws.*;
import java.io.*;
import java.net.URL;
import javax.xml.bind.JAXBElement;
import javax.xml.namespace.QName;

public class WsClient {

  private final static String DOCUMENTCONVERTERSERVICE_WSDL_LOCATION = "https://localhost:41734/Muhimbi.DocumentConverter.WebService/?wsdl";

  private static ObjectFactory _objectFactory = new ObjectFactory();

  public static void main(String[] args) {
    try {
      if (args.length == 0) {
        System.out.println("Please specify one or more file names to convert and merge.");
      } else {
        System.out.println("Merging files");

        // ** Initialise Web Service

        DocumentConverterService_Service dcss = new DocumentConverterService_Service(new URL(DOCUMENTCONVERTERSERVICE_WSDL_LOCATION), new QName("https://tempuri.org/", "DocumentConverterService"));
        DocumentConverterService dcs = dcss.getBasicHttpBindingDocumentConverterService();

        // ** Get the options for all files that need to be merged

        ProcessingOptions processingOptions = getProcessingOptions(args);

        // ** Carry out the merging (and converting if needed)

        BatchResults results = dcs.processBatch(processingOptions);

        // ** Get the content of the first file, which holds the merged file in the byte array

        byte[] convertedFile = results.getResults().getValue().getBatchResult().get(0).getFile().getValue();

        // ** Write converted file to file system

        writeFile(convertedFile, "merged.pdf");
        System.out.println("Files merged into 'merged.pdf'");
      }

    } catch (IOException e) {
      System.out.println(e.getMessage());
    } catch (DocumentConverterServiceProcessBatchWebServiceFaultExceptionFaultFaultMessage e) {
      printException(e.getFaultInfo());
    }
  }

  public static ProcessingOptions getProcessingOptions(String[] sourceFileNames) throws IOException { // ** Options and all settings for batch conversion

    ProcessingOptions processingOptions = new ProcessingOptions();

    // ** Specify the minimum level of merge settings, you can optionally add watermarks and security settings

    MergeSettings mergeSettings = new MergeSettings();
    mergeSettings.setBreakOnError(false);
    processingOptions.setMergeSettings(_objectFactory.createProcessingOptionsMergeSettings(mergeSettings));

    // ** Create an array of files to merge

    ArrayOfSourceFile sourceFiles = new ArrayOfSourceFile();
    for (int i = 0; i < sourceFileNames.length; i++) {
      SourceFile sourceFile = getSourceFile(sourceFileNames[i]);
      sourceFiles.getSourceFile().add(sourceFile);
    }

    processingOptions.setSourceFiles(_objectFactory.createProcessingOptionsSourceFiles(sourceFiles));
    return processingOptions;
  }

  public static SourceFile getSourceFile(String fileName) throws IOException {
    File file = new File(fileName);

    // ** Read the contents of the file

    System.out.println("- Reading: " + fileName);
    byte[] sourceFileContent = readFile(fileName);

    // ** Set the absolute minimum open options

    OpenOptions openOptions = getOpenOptions(getFileName(file), getFileExtension(file));

    // ** Set the absolute minimum conversion settings.

    ConversionSettings conversionSettings = getConversionSettings();

    // ** Create merge settings for each file and set the name for the PDF bookmark

    FileMergeSettings fileMergeSettings = new FileMergeSettings();
    fileMergeSettings.setTopLevelBookmark(_objectFactory.createFileMergeSettingsTopLevelBookmark(file.getName()));

    // ** Create a source file object and return it

    SourceFile sourceFile = new SourceFile();
    sourceFile.setOpenOptions(_objectFactory.createSourceFileOpenOptions(openOptions));
    sourceFile.setConversionSettings(_objectFactory.createSourceFileConversionSettings(conversionSettings));
    sourceFile.setMergeSettings(_objectFactory.createSourceFileMergeSettings(fileMergeSettings));
    sourceFile.setFile(_objectFactory.createSourceFileFile(sourceFileContent));
    return sourceFile;
  }

  public static OpenOptions getOpenOptions(String fileName, String fileExtension) {
    OpenOptions openOptions = new OpenOptions(); // ** Set the minimum required open options. Additional options are available

    openOptions.setOriginalFileName(_objectFactory.createOpenOptionsOriginalFileName(fileName));
    openOptions.setFileExtension(_objectFactory.createOpenOptionsFileExtension(fileExtension));
    return openOptions;
  }

  public static ConversionSettings getConversionSettings() {
    ConversionSettings conversionSettings = new ConversionSettings(); // ** Set the minimum required conversion settings. Additional settings are available

    conversionSettings.setQuality(ConversionQuality.OPTIMIZE_FOR_PRINT);
    conversionSettings.setRange(ConversionRange.ALL_DOCUMENTS);
    conversionSettings.getFidelity().add("Full");
    conversionSettings.setFormat(OutputFormat.PDF);
    return conversionSettings;
  }

  public static String getFileName(File file) {
    String fileName = file.getName();
    return fileName;
  }

  public static String getFileExtension(File file) {
    String fileName = file.getName();
    return fileName.substring(fileName.lastIndexOf('.') + 1, fileName.length());
  }

  public static byte[] readFile(String filepath) throws IOException {
    File file = new File(filepath);
    InputStream is = new FileInputStream(file);
    long length = file.length();
    byte[] bytes = new byte[(int) length];

    int offset = 0;
    int numRead;
    while (offset < bytes.length && (numRead = is.read(bytes, offset, bytes.length - offset)) >= 0) {
      offset += numRead;
    }

    if (offset < bytes.length) {
      throw new IOException("Could not completely read file " + file.getName());
    }
    is.close();
    return bytes;
  }

  public static void writeFile(byte[] fileContent, String filepath) throws IOException {
    OutputStream os = new FileOutputStream(filepath);
    os.write(fileContent);
    os.close();
  }

  public static void printException(WebServiceFaultException serviceFaultException) {
    System.out.println(serviceFaultException.getExceptionType());
    JAXBElement < ArrayOfstring > element = serviceFaultException.getExceptionDetails();
    ArrayOfstring value = element.getValue();
    for (String msg: value.getString()) {
      System.out.println(msg);
    }
  }

}